Television, since its introduction into the commercial markets, has become a ubiquitous product that has reached into every comer of daily life. Television, whether broadcast television or cable television, provides viewers with more information about changes in the world than any other news form or media. As such the number of televisions sets that are in operation is in the hundreds of millions.
Current television technology, termed Standard Definition Television (SDTV), is based on an analog technology that was developed and standardized in the mid-portion of the 20th century. These long established television broadcast standards for frequency allocation, format, etc., impose limits upon the amount of information that can be transmitted and, consequently, viewed by a user. Newer digital television technology, termed High Definition Television (HDTV), designed to overcome the limitations of SDTV, is able to increase the amount of the data transmitted by digitizing and compressing the television signal before transmission. A significant advantage of HDTV over SDTV is that the increased data transmission improves the clarity of the viewed image. The clarity is improved by transmitting an image having greater resolution than SDTV transmission.
As the number of HDTV transmissions begin to increase in conjunction with the existing SDTV transmissions, hundreds of millions of SDTV television sets must be adapted to receive the new HDTV signals. Adapting SDTV television sets to HDTV formats may be easily accomplished by adding a converter box, e.g., a set-top box, to spatially downscale the received HDTV signal to a format acceptable for viewing on the SDTV television set. Techniques to spatially downscale from HDTV to SDTV are well known in the art.
WO97/14252-A1 discloses a method and apparatus using the discrete cosine transform (DCT) to resize the image. To reduce an image, the method and apparatus exploit the convolution-multiplication property of the DCT to implement the anti-aliasing filter in the DCT domain, then the filter coefficients are operated on to produce DCT coefficients of the reduced-size image.
EP 0 781 052-A2 discloses a decoder for decoding MPEG video bitstreams encoded in any color space encoding format and outputting the decoded video bitstream to different size windows. Both MPEG decompression and color space decoding and conversion are performed on the bitstreams within the same decoder. The disclosed decoder may be programmed to output the decoded video bitstream in any of three primary color space formats comprising YUV 4:2:0, YUV 4:2:2 and YUV 4:4:4. The decoder may also output the decoded bitstream to different sized windows using DCT based image resizing.